Inflammatory diseases and disorders are conditions in which an abnormal or otherwise deregulated inflammatory response contributes to the etiology or severity of disease. Examples include autoimmune diseases such as type 1 diabetes and Celiac disease.
Many of these diseases are characterized by a mononuclear cell infiltration at a site of tissue injury or other insult. Examples of mononuclear cells that have been observed in these infiltrations include lymphocytes, especially T lymphocytes, and cells of the mononuclear phagocyte system (MPS cells) such as monocytes, macrophages, dendritic cells, microglial cells and others.
Many of the cells observed in the mononuclear cell infiltrates are suspected of having a role in these abnormal inflammatory responses. For example, in diseases such as multiple sclerosis, CD4+ T cells are known to play a central role in the pathologic autoimmune response. At an earlier time point in T cell activation, dendritic cells and other MPS cells may be responsible for activation of CD4+ T cells. MPS cells could also contribute to inflammation through phagocytosis although in at least some inflammatory diseases it is not clear whether such cells would be capable of this in the absence of CD4+ T cells.
Peripheral blood monocytes may be classified into one of two groups according to the expression or not of certain cell surface molecules. In particular, human “resident monocytes” or “mature monocytes” are understood to have a CD14loCD16+ phenotype (the mouse counterpart is CX3CR1hiCCR2−Gr1−). Another group of cells, the “inflammatory monocytes” or “immature monocytes” are understood to have a CD14+CD16− phenotype (the mouse counterpart is CX3CR1loCCR2+Gr1+). (Geissmann F. et al. 2003 Immunity 19: 71-82)
Importantly, while the latter are understood to be “inflammatory” in the sense that they are observed to migrate into inflamed tissue from bone marrow derived peripheral blood cells, these cells have not been shown to cause inflammation either directly or through the action of other cells. Further, the various MPS cells that may be formed when these cells differentiate have also not been shown to cause inflammation.
Conventional clinical strategies for general long-term immunosuppression in disorders associated with an undesired immune response are based on the long-term administration of broad acting immunosuppressive drugs, for example, signal 1 blockers such as cyclosporin A (CsA), FK506 (tacrolimus) and corticosteroids. Long-term use of high doses of these drugs can have toxic side-effects. Moreover, even in those patients that are able to tolerate these drugs, the requirement for life-long immunosuppressive drug therapy carries a significant risk of severe side effects, including tumors, serious infections, nephrotoxicity and metabolic disorders.
Methods of inducing antigen-specific tolerance have been developed, including cell coupling of an antigen or peptide. For example, in one method, peptide induced cell coupled tolerance involved collection, separation and treatment of peripheral blood cells with disease specific autoantigens and the ethylene carbodimide (ECDI) coupling reagent under sterile conditions, and subsequent re-infusion into the donor/patient. This process is costly and must be conducted under closely monitored conditions by skilled practitioners and is limited in the number of centers that can conduct the procedure. The use of red blood cells as the donor cell type expands the potential source to include allogeneic donors thus increasing the supply of source cells dramatically and potentially expanding the delivery of this therapy to any setting certified for blood transfusion. These approaches have significant limitations in terms of supply of source cells and necessity for tissue type matching to minimize immune response to the donor cells. In addition the local treatment of the cells to couple autoantigens via EDCI presents a significant quality control issue. Furthermore, these approaches also require at least some knowledge of the pathological antigen for which immune tolerance is sought.
Recently, peptide-coupled particles have been described which eliminates the requirement for a supply of source cells and circumvents the tissue-typing requirement of the prior approaches, See WO 2010/085509, incorporated by reference herein in its entirety. Not withstanding, the use of antigens coupled to the outside of particles is associated with increased anaphylaxis and has significant chemistry, manufacturing and control issues. Surprisingly, when the antigen is encapsulated within the particle, these adverse events are avoided. Even more surprisingly, the size and the charge can be altered to enhance tolerance to specific antigens.
Antigen-specific tolerance is generally not ideal because specific antigens/epitopes are generally not known in human diseases. Furthermore, antigens can vary from subject to subject in order for an antigen specific approach to be effective, therefore it would be necessary to determine which antigens each individual patient would recognize, or it would require coupling a library of possible peptides to the particles prior to administration. The synthesis and individual coupling of these peptides is both time consuming and expensive. Therefore, a need exists for a therapy which solves both of these problems thereby eliminating the need to for a source of tissue matched cells.